Telephone-exchange system



L. W. CARROLL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT.14.19IT- 1,324, 796. Patented Dec. 16,1919.

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LOUIS W. CARROLL, OE RIVERSIDE, ILLINOIS, ASSIGNOB, T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEH/V YORK, N. Y., A CORPORATION -.OF NEW 1 YORK.

TELEPHONE-EXCI-IAN GE SYSTEM.

Specification of Letters Patent. Patented Dec. 16, 1919.

Application filed September 14, 1917. Serial No. 191,354.

To all whom it may concern:

Be it known that I, LoUIs W. CARROLL, a

"citizen of the United States, residing at Riverside, in the county of Cook and State of Illinois, have invented certain new and useful ImprovementsinTelephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone eX- change systems, and more particularly to such systems of the central ofiice type.

The object of this invention is to provide a system of this character in which an operators telephone set is automatically connected to and disconnected from a calling telephone line, and a source ofringing current is automatically connectedto and disconnected from a'called line with a minimum amount of apparatus.

In accordance with this invention, there is provided a link circuit equipped with four relays, two of which are supervisory relays and the other two, one a ringing relay and the second a tripping relay. One of the supervisory relays and the ringing relay, cooperate to control the connection of the operators telephone set to the link circuit. The supervisory relay associated with the answeringend of the link circuit also cooperates with the tripping and ringing relays to disconnect ringing current from the called line when a call is abandoned by the calling party.

For a more complete understanding of this invention, reference should be had tothe following description considered in connection with the accompanying drawing contaming one embodiment of this invention.

In the drawing there are shown two telephone lines, A and B, which terminate at a central office, at which is located a cord circuit C for interconnecting these lines.

observing the lighted condition of line lamp 6, inserts answering plug 7 'into line jack 8,

whereupon cut-01f relay 10 is operated over a circuit from battery through the lower normal contact of answering supervisory relay 9', answering supervisory lamp 11 sleeve contacts of the answering plug 7 and 'jack 8, and the winding of cutoft' relay 10 to ground. Cut-ofi relay 10 in operating disconnects the line relay 5 from the line, whereupon the line relay releases, extinguishing the line lamp 6. Supervisory lamp 11 would light were it not for the fact that the answering supervisory relay 9 is also actuated upon the connection or" the answering plug with the line jack, thereby connecting resistance 12 in circuit with the lamp 11 and preventing the lamp from presenting a signal. Answering supervisory relay 9 is energized over a circuit from battery through the lower winding of this relay, ring contacts of the answering plug? and line jack 8, over one side of the'line, through the substation apparatus, back over the other side of the line,'tip contacts of linejack 8 and answering plug 7 and 'the upper winding of relay 9 to ground. Answering supervisory relay 9 in addition to preventing the lighting of supervisory lamp 11, connects the operators telephone set to the'talking strands of the cord circuit and thence to the calling line A.

The-operator upon being advised that the calling subscriber A desires to be connected with the line of subscriber B, inserts calling plug 17 into line jack 18, thereby causing the energization of ringing relay 19 and cut-off relay 20 over a circuit from battery through the lower alternate contact of answering supervisory relay 9, normal contact of tripping relay 21, winding of ringing relay 19, sleeve contacts of the calling plug 17 and line ack 18, andthe winding of cut-oil relay 20 to ground. The energizationoit cut-0ft relay 20 disconnects line relay 2-2 from line B. Calling supervisory lamp 23 is also lighted overa circuit from battery through the normal contact of calling supervisory relayfZl, lamp 23, sleeve contacts of the calling plug 17 and line jack 18, and the winding of cut-ofi relay 20 toground. Ringing relay 19 is of the so called two-step type which, when fully energized, operates all of its contacts and when partially energized, actuates only a portion of its contacts. This ringing relay 19 is designed and adjusted so that of the cord circuit.

when it is fully energized over the hereinbefore traced circuit, it opens all of its normal contacts and closes its alternate contacts. The opening of its normal contacts '30 and 31 disconnects the operators telephone set from the talking strands of the cord circuit. The opening of its normal contacts 32 and 33 introduces breaks in the talking strands of the cord circuit, and the closure of its alternate contacts connects a source of ringing current 35 to line This circuit for ringing current may be traced from the source of ringing current 35 through the lower winding of tripping relay 21, lower alternate contact of ringing relay 19, ring contacts of the calling plug 17 and line jack 18, over one side of the line B, through call bell 36 and condenser 37 back over the other side of line B, tip contacts of the line jack 18 and calling plug 17, and the upper alternate contact of ringing relay 19 to ground. Gurrent traversing this path causes the operation of call bell 36. The called party in response to the Operation of call bell 36, removes the receiver from the switohliook, thereby establishing a lower resistance path for the ringing current from source 35, whereupon tripping relay 21 is energized. Upon the enen gization of this tripping relay 21, its contact is opened, thereby removing the short circuit of the upper winding of tripping relay 21 which is thereupon included in circuit with the winding of ringing relay 19.

The inclusion oi": the upper winding of tripping relay 21 in circuit with the ringing relay 19 causes a reduced flow of current through ringing relay 19, consequently a partial de'energization thereof, whereupon ringing relay 19 actuates over a portion of its contacts. The contacts actuated are the upper and lower alternate contacts which are opened, and the normal contacts 32 and 33 which are closed; the opening of the alternate contacts disconnecting the source of ringing current from the called line, and the closure of the normal contacts 32 and 33 closing the breaks in the talking strands The closure of contacts and 33 connects the calling supervisory relay 24 in circuit with the called line, which thereupon operates to include resistance 4L0 in circuit with the calling supervisory lamp 23, which is thereby extinguished. Ringing relay 19, when only partially energized, as when the upper winding of tripping relay 21 is in circuit therewith maintains its normal contacts 30 and 31 open, thereby maintaining the operators telephone set disconnected from the cord circuit.

Upon the conclusion of the conversation,

subscribers A and B restore the receivers to the 'switchhooks, causing the release of both supervisory relays which thereupon short-circuit the resistances 12 and 40, permitting both supervisory lamps 11 and 23 to be lighted to furnish disconnection signals. The operator may thereupon withdraw the plugs from the jacks, whereupon all apparatus is restored to normal position.

it, while the answering plug of the cord circuit is connected with line A, the receiver of which is off the switchhook, and the calling plug is connected with line B, the receiver of which has not been removed from the switchhook, and the calling subscriber A abandons the call, ringing current is thereby automatically disconnected from the called line B. This is brought about in the following manner.

Subscriber A in restoring the receiver to the switchhook causes the deenergization of answering supervisory relay 9, which thereupon opens its lower alternate contact which is in the short cir uit of the upper winding of the tripping relay 21. This upper winding of tripping relay 21 is thereupon included in circuit with the ringing relay 19 to cause the partial denergization of this ringing relay in the manner hereinbe'fore described. Ringing current is thereby disconnected from the called line in the manner hereinbefore described. Upon the release of the answering supervisory relay 9, answering supervisory lamp 11 is lighted to furnish a disconnect signal. Calling supervisory lamp 23 is also lighted at this time, so that the operator upon observing the lighted condition of both lamps may withdraw the plugs from the jacks.

That is claimed is:

1. A telephone exchange system comprising telephone lines, a link circuit for interconnecting the lines, a source of ringing current, a ringing relay energized to one degree due to the connection of the link circuit with one of the lines to connect therewith the source of ringing current, and means effective upon the response of the called line for causing the energization of the ringing relay to another degree thereby to disconnect the source 01" ringing current from the called line.

2. A telephone exchange system comprising telephone lines, a link circuit for interconnecting the lines, a source of ringing current, a ringing relay energized to one degree upon the connection of the link circuit with one of the lines to connect therewith the source 01" ringing current, and a relay actuated upon the response of the called line for causing the energization of the ringing relay to another degree thereby to disconnect the source of ringing current from the called line.

3. A telephone exchange'system comprising telephone lines, a link circuit for interconnecting the lines, a source of ringing current, a ringing relay energized to one degree upon the connection of the link circuit with .one of the lines to connect therewith the source of ringing current, a tripping relay in circuit with the source of ringing current I energized upon the response of the called line, and a resistance connected in circuit with the ringing relay. upon the energization of the tripping relay thereby to cause the partial deenergization of the ring ing relay whereby the source of ringing current is disconnected from the called line.

4:. A telephone exchange system comprising telephone lines, a link'circuit for interconnecting the lines, a source of ringing current, a ringing relay fully energized upon the connection of the link circuit with one of the lines to connect therewith the source of ringing current, a tripping relay having a winding in circuit with the source of ringing current for energizing the tripping relay upon the response of the called line, and a second winding for the tripping relay in cluded in circuit with the ringing relay upon the energization of the tripping relay thereby causing the partial denergization of the ringing relay, whereby the source of ringing current is disconnected from the called line.

5. A telephone exchange system comprisingtelephone lines,-a link circuit for interconnecting the line, an operators telephone set, arelay in the answering'end of the link circuitenergized-upon the connection of the answering end of the link circuit with a-calling line to connect therewith the operators telephone set, a source of ringing current,'a ringing relay energized to one degree upon the connection of the link circuit with another line to connect therewith a source of ringing current, and means effective upon the response of the called line to cause the energization of the ringing relay to another degree thereby to disconnect the ringing cur rent from the called line.

6. A telephone exchange system comprising telephone lines, a link circuit for interconnecting the lines, an operators telephone set, a supervisory relay in the link circuit energized upon connection of the link circuit with the calling line to connect therewith the operators telephone set, a source of ringing current, a ringing relay energized to one degree due to the connection of the link circuit with another line to connect therewith the source of ringing current, and means eflective upon the response of the called line to cause the energization of the ringing relay to another degree thereby to disconnect the source of ringing current from the called line. Y

7. A telephone exchange system comprising telephone lines, a link circuit for interconnecting the lines, an operators telephone set, a supervisory relay in the link circuit energized upon connection of the link circuit withthe calling line to connect there with the operators telephone set, a source of ringing current, a ringing relayl energized'to one degree upon connection of the link circuit with another line to connect therewith the source of ringing current, and a relay energized upon the response of the called line thereby to cause the energization of the ringing relay to another degree, whereby the source of ringing current is disconnected from the called line.

8. A telephone exchange system, comprising telephone lines, a link circuit for interconnecting the lines, an operators telephone set, a relay in the link circuit energized upon connection thereof with a calling line to connect therewith the operators telephone set, a source of ringing current, a ringing relay energized to one degree upon connection of the link circuit with another line to connect therewith the source of ringing current, a tripping relay in circuit with the source of ringing current and actuated upon the response of thecalled line, and a resistance connected in circuit with the ringing relay upon the actuation of the tripping relay thereby to cause the energization of the ringing relay to another degree, whereby the source of ringing current is disconnected from the called line. i v

9. A telephone exchange system comprising telephone lines, a link circuit for inter: connecting the lines, an operators telephone set, a relay responsive to the connection of the link circuit witha calling line to connect therewith the operators telephone set, a source of ringing current, a ringing relay fully energized upon connection 01"- the link circuit with another line to connect therewith the source of ringing current, a tripping relay having a winding in circuit with the source of ringing current for energizing the tripping relay upon the response of the called line, and another winding for the tripping relay brought into circuit with the ringing relay upon the energization ofthe tripping relaythereby to cause the partial deenergization of the ringing relay, where-- by the source of ringing current is disconnected from the called line.

10. A telephone exchange system com rising telephone lines, a link circuit connected with one of the lines as a calling line, a source of ringing current, a ringing relay energized to one degree upon the connection of-the link circuit with another line to connect therewith the, source of ringing current,

ing telephone lines, a link circuit connected with one of the lines as a calling line, a relay in the link circuit controlled from the calling line, a source of ringing cur-rent, a ringing relay energized to one degree upon connection of the link circuit with another line to connect therewith the source or" ringing cur rent, and the relay efiective upon the deenergization of the relay. controlled from the calling line for causing the energization of the ringing relay to another degree thereby to disconnect the source of ringing current from the called line.

12. A telephone exchange system comprising telephone lines, a link circuit connected with one of the lines as a calling line, a supervisory relay in the link circuit controlled from the calling line, a source of ringing current, a ringing relay fully energized upon connection of the link circuit with another line to connect therewith a source of ringing current, and a resistance included in circuit with the ringing relay upon the deenergization of the supervisory relay for causing the partial deenergization of the ringing relay thereby to disconnect the source of ringing current from the-called line.

13. A telephone exchange system comprising telephone lines, a link circuit connected with one of the lines as a calling line a supervisory relay in the link circuit controlled from the calling line, a source of ringing current, a ringing relay fully energised upon connection of the link circuit with another line to connect therewith the source of ringing current, and a third relay normally short-circuited while the supervisory relay is energized over a calling line and brought into circuit with the ringing relay upon the deenergization of the supervisory relay to cause the partial denergization of the ring ing relay thereby to disconnect the source of ringing current from the called line.

14. A telephone exchange system comprising telephone lines, a link circuit connected with one of the linesas a calling line, a supervisory relay in the linkcircuit controlled from the calling line, a source of ringing current, a ringing relay energized to one degree upon connection of the link circuit with another line .to connect therewith the sounceoi ringing current and means ell'ec tive upon either the dee-nergization of the supervisory relay or upon the response of the called line for causing the energization of the ringing relay to anotherldegree thereby to disconnect the source of ringing current from the called line.

15. A telephone exchange system comprising telephone lines, a link circuit connected with one or" the lines as a calling line, a supervisory relay in the link on cuit controlled from the calling line, a source cl ringing current, a ringing relay energized to one degree upon connection of the link circuit with another line to connect therewith the source of ringing current, and a relay effective upon either the deenergization of the supervisory relay or upon the response of the called line for causing the ,energization of the ringing relay to another degree thereby to disconnect the source of ringing current from the called line.

16. A telephone exchange system comprising telephone lines, a link circuit connected with one of the lines as a calling line, a supervisory relay in the link circuit controlled from the calling line, a source of ringing current, a ringing relay energized to one degree upon connection of the link circuit with another line to connect therewith the source of ringing current, and a tripping relay in circuitwith the source of ringing current and energized upon the response of the called line, and a resistance coil included in circuit with the ringing relay upon either the deenergization of the supervisory relay or the energization of the tripping "relay for causing the energization of the ringing relay to another degree thereby to disconnect the source of ringing'current from the called line.

In witness whereof, I hereunto subscribe my7name this 27th day of August, A. D.. 191 a.

LOUIS W. CARROLL 

